US2814256A - Rotary pumps of the non-centrifugal type - Google Patents

Description

Nov. 26, 1957 F. w. MOCOMBIE ROTARY PUMPS OF THE NON-CENTRIFUGAL TYPE 2 Sheets-Sheet 1 Filed March 15, 1954 INVENTOR fFPQE/P/c/rMz P/VcCO/VBM Nov; 26, 1957 F. w; MQCOMBIE 2,814,256

v ROTARY Pumps OF THE NON-CENTRIFUGAL TYPE Filed March 15. 1954 v 2 Sheets-Sheet 2 FIG-.3.

INVENTOR United States Patent C F ROTARY PUMPS on THE NON-CENTRIFUGAL TYPE Frederick Walter McCombie, London, England, assignor to Megator Pumps & Compressors Limited, London, England Application March 15, 1954, Serial No. 416,006

Claims priority, application Great Britain March 24, 1953 8 Claims. (Cl. 103-463) This invention relates to rotary pumps of the noncentrifugal type, examples of such pumps forming the subject of our prior U. S. Patents Nos. 2,561,808; 2,561,809; 2,561,810; 2,612,846; 2,728,615 and 2,750,896. Such pumps include as working parts a displacement chamber generally referred to as a shoe containing an eccentrically mounted disc which is rotatably mounted therein to impart a reciprocating movement to the shoe in the plane of rotation of the disc to open and close inlet and outlet ports in a port plate over which the shoe slides and to provide the necessary displacement effect, the disc engaging the walls of the shoe at two oppositely disposed points on its periphery and also at the sides to provide a substantially fluid tight seal, the shoe and its associated disc being carried by a driving shaft mounted within the outer casing, the shoe being situated on the high pressure side of the pump, the pressure of the fluid being pumped serving to maintain the shoe in a fluid tight connection with the port plate with which it is slidably associated. Such pumps include either a single shoe or a plurality thereof, for example, three and the chief object of the present invention is to reduce the bending moment in the disc carrying shaft generally referred to as the rotor shaft resulting from the side thrust imposed on the shaft by each disc during its working stroke owing to the difference in fluid pressure between the inside and outside of the shoe.

In this connection it will be appreciated that it is desirable, if possible, to avoid the use of an intermediate hearing or bearings for the rotor shaft but in the case of a pump which includes, for example, four or more shoes and utilising only two bearings at opposite ends of the shaft the length of shaft which is unsupported is quite long.

A rotary pump of the non-centrifugal type including a plurality of shoes each mounted for reciprocating movement over a port plate under the action of an eccentric disc, all the eccentric discs being associated with a common shaft is characterised according to the invention in that the shoes are so positioned around the axis of the shaft as to balance out or substantially balance out any bending forces to which the shaft is subjected during operation.

It is preferred that the shoes shall be so arranged that some of them lie on one side of the shaft the remainder being arranged on the opposite side, the shoes on opposite sides facing in diametrally opposite directions.

It is, however, within the scope of the invention to arrange the shoes in any other way which will produce the desired result. For example, the shoes on one side of the shaft may be arranged at an angle with respect to the shoes on the opposite side, the angle being a large one and between 90 and 180 so that the bending forces on the shaft will be balanced out to a substantial extent.

As a further alternative the shoes may be equidistantly spaced about the axis of the shaft although such an arrangement might lead to difficulties in construction.

2,814,256 Patented Nov. 26, 1957 It is preferred to use four or six shoes arranged in pairs. In the case of four shoes being employed, one pair will be arranged on one side of the shaft and the other pair will be arranged on the opposite side. If six shoes are used then one pair, for example, the central pair, will be arranged on one side, whilst the outside pairs will be arranged on the opposite side.

It is preferred that the discs comprising each pair shall be eccentrically arranged in diametrally opposite directions and that all the discs associated with the rotor shaft shall be arranged in equally spaced angular positions about the axis of the rotor shaft.

When arranging the discs as pairs each pair may be associated with a common port plate, the plate being formed with two sets of ports for co-operating with each shoe.

It will be appreciated that when using two oppositely facing shoes or in an arrangement in which one or more sets of shoes face the opposite way to the remaining set or sets, two oppositely positioned port plates will be required which will be situated in the pump casing on opposite sides of the rotor shaft, the port plates being staggered lengthwise of the shaft. It is found in practice that this part or complete balancing of the bending forces or side thrust on the rotor shaft enables a shaft to be constructed of smaller diameter, this in turn permitting of greater eccentricity of the discs of a particular diameter, the total elfect being to produce a lighter and cheaper rotor for a given capacity and pressure. This construction also reduces the resultant side thrust on the bearings of the rotor so cheapening the bearings and reducing friction and wear.

Furthermore it obviates the necessity or desirability of supporting the shaft between its ends by intermediate bearings even though the shaft may be of considerable length.

It is found that the arrangement of six shoes described above greatly reduces the shaft stresses as compared with an arrangement having all the shoes facing the same way owing to the partial balancing of the forces involved. At the same time owing to the fact that four shoes face one way and two the other way, the resultant side thrust on the rotor shaft is always in the same direction. This arrangement has the additional advantage of helping to maintain the lubricating film in the bearings and enabling the rotor to run smoothly even though the bearings are a very loose fit.

Referring to the drawings:

Figure 1 is a longitudinal vertical section of a pump in accordance with the invention;

Figure 2 is a longitudinal horizontal section of the same;

Figure 3 is a cross-section.

The invention will hereinafter be described in detail as applied to a pump which includes three pairs of shoes, namely a centrally positioned pair and two end pairs making six shoes in all.

In the construction illustrated the pump comprises a body or casing 1 forming a pressure chamber 1 carrying at its end bearings 2 and seals 3 for a rotor shaft 4 carrying eccentric discs 5, the rotor shaft carrying a coupling drum 6 through the medium of which the rotor shaft is driven from a suitable source of power supply.

The casing carries three main covers 7 forming suction chambers 8 which communicate with a common supply chamber 10 having an inlet 10 for the admission of the liquid which is being pumped. The three main cov ers 7 are also formed with discharge passageways 9 which communicate through openings 9' with the pressure chamher 1' which is provided with a discharge outlet (not shown), the pressure in the chamber 1' being higher than at the suction side.

Each disc revolves in a shoe 11 which is preferably composed of a comparatively resilient mouldable material such as a natural or synthetic rubber or incorporates a lining composed of such material, the shoe fitting the disc on its opposite faces and also at two opposite points on its periphery. The arrangement is such that as a result of rotation of the disc the shoe will be reciprocated vertically over the face of a port plate 12 carried by the adjacent cover 7.

Each port plate 12 is formed with two sets of laterally spaced suction and discharge ports one set being provided for each shoe there being in each set two suction ports 13 which communicate with the interior of the cover 7 and two discharge ports 14 which lead to the interior of the main body 1 of the pump. The pressure in the chamber 1, being higher than the pressure in the ports 13 and covers 7, tends to hold all the shoes in good sealing engagement with the faces of the port plates 12.

Each shoe 11 is formed with a pair of ports 15 which perform the functions of both suction and discharge ports and communicate alternately with ports 13 and 14 under the reciprocating action of the shoe. The effective internal volume of the shoe is varied as a result of rotation of the disc and consequently the shoe acts as a displacement chamber, the liquid being drawn into the interior of the shoe through the ports 13 and when ports 14 and 15 are in register being discharged through ports 14 and into the chamber 1 from which it is finally discharged.

The two discs 5 of the centre pair are arranged at 180 to one another, the two discs of each outer pair being also at 180 to one another and the outer pairs at 120 and 240 respectively to the centre pair. This clearly places the six discs in equally-spaced angular positions with their working strokes occurring in regular sequence and results in a smooth displacement of fluid and an even turning moment.

This arrangement of six shoes has another advantage over the commonly used design employing three shoes, namely, that there are two shoes functioning at every point in the cycle, whereas with three shoes at 120, although the theoretical combined displacement curve is practically as smooth as with the six shoes, it is the resultant of two shoes functioning during parts of the cycle and only one shoe during other parts. The actual displacement of the liquid is equivalent to the theoretical combined displacement of the shoes less the leakage or slip, and this leakage is twice as great when two shoes are functioning as when one only is functioning. Thus the three shoe pump introduces in practice an irregularity of flow that is absent from the six shoe pump in which there are always two shoes functioning at one time.

The shoes shown are of the known type, as disclosed by the specifications and drawings of the earlier patents hereinbefore referred to, each shoe being of substantially U shape and being cut away to clear the rotor shaft, the limbs being connected by one or more bolts and tubular distance pieces.

I claim:

1. A rotary pump comprising a casing defining a pressure chamber and a supply chamber, a rotor shaft mounted in said casing and extending through said pressure chamber, said casing including a plurality of port plates equally spaced from the axis 'of said shaft, the inner surfaces of said port plates having planar slideways and each having a suction port in communication with said supply chamber and a discharge port in communication with said pressure chamber, a plurality of discs eccentrically mounted on said shaft within said pressure chamher, and a hollow shoe fitting each disc and engaging a slideway of one of said port plates to be reciprocated thereover by rotation of the disc for alternate communication with said suction and discharge ports, each shoe closely surrounding each disc diametrically thereof in a plane parallel to the respective slideway and forming a pumping chamber between the periphery of the disc and the port plate, said port plates being substantially equally spaced angularly around said shaft to distribute the thrust imposed on the shaft by each disc during its working stroke and reduce the bending moment in said shaft.

2. A rotary pump as set forth in claim 1 wherein each port plate is provided with two sets of laterally spaced suction and discharge ports, one set for each shoe, each shoe having a pair of ports communicating alternately with the suction and discharge ports of the plate.

3. A rotary pump as set forth in claim 1, wherein some of the shoes and port plates are arranged on one side of the shaft while the remainder of the shoes and port plates are arranged on the opposite side of the shaft.

4. A rotary pump as set forth in claim 1, wherein the shoes are arranged in pairs spaced apart throughout the length of the shaft, so that the working strokes occur in regular sequence and results in a smooth displacement of fluid and in even turning moment of the shaft.

5. A rotary pump as set forth in claim 4, wherein each pair of shoes cooperate with a common port plate.

6. A rotary pump as set forth in claim 1, wherein the discs are arranged in equally spaced angular positions about the axis of the shaft.

7. A rotary pump as set forth in claim 3, wherein the shoes are arranged in three pairs, the central pair engagging port plates on one side of said shaft and the two outside pairs engaging port plates on the opposite side of said shaft.

8. A rotary pump as set forth in claim 3, wherein the shoes are arranged in pairs along the length of the shaft, one pair of shoes engaging port plates on one side of said shaft and another pair of shoes engaging port plates on the opposite side of said shaft.

References Cited in the file of this patent UNITED STATES PATENTS

Images